Collapsible stroller frame



FIG. 1 is an isometric view of a collapsible stroller frame;

FIG. 2 is a front elevation view of the collapsible stroller frame;

FIG. 3 is a rear elevation view of the collapsible stroller frame;

FIG. 4 is a left side elevation view of the collapsible stroller frame;

FIG. 5 is a right side elevation view of the collapsible stroller frame;

FIG. 6 is a top plan view of the collapsible stroller frame; and,

FIG. 7 is a bottom view of the collapsible stroller frame.

The broken lines in the drawings represent portions of the collapsible stroller frame which are not part of the claimed design. 

CLAIM The ornamental design for a collapsible stroller frame, as shown and described. 